Tone oscillator for an electronic musical instrument

ABSTRACT

A plurality of frequency dividers are connected in series with an oscillator having a fundamental frequency. The outputs obtained from the frequency dividers are applied to a plurality of L-C oscillating circuits. Each L-C oscillating circuit produces a sinusoidal and a complex output signal which are combined to obtain a musical tone.

nited States awn [151 3,639,853 Sakai 1 Feb. 1, 1972 [54] TONE OSCILLATOR FOR AN ELECTRONIC MUSICAL INSTRUMENT References Cited [72] Inventor: Tadao Sakai, No. 767-11, Uenoshiba, Mu UNITED STATES PATENTS f Osaka 2,777,064 1/1957 Robinson ..331/38 apan [22] Filed: Aug. 21, 1970 Primary ExaminerJohn Kominski PP Noz 65,806 Att0meyKurt Kelman ABSTRACT [30] Foreign Application Priority Data A plurality of frequency dividers are connected in series with Mar. 27; 1970 Japan ..45/26192 Oscillator having a fundamental q y- The outputs obtained from the frequency dividers are applied [52] US. Cl ..331/51, 84/].01, 331/52, to a plurality of L C oscillating cilcuha Each L C oscillating 331/55 331/56 331/61 331/117 circuit produces a sinusoidal and a complex output signal [51 Int. Cl. ..H03b 5/08 which are combined to obtain a musical tone [58] FieldofSearch .331/117,38, 39,51,52, 55,

331/56, 61; 328/25, 30; 84/101, DIG. 11; 307/220 3 Claims, 2 Drawing Figures MAIN OSCILLATOR 2 H) OSCILLATOR 2A FREQUENCY OIVIOER 35 v I 3 H) OSCILLATOR fJA FREQUENCY DIVIOER 038 H OSCILLATOR P 4/4 FREQUENCY 4 OIVIDER 48 l o L-O OSOILLAERJA FREQUENCY OIVIOER 56 PATENIED FEB I 1972 I MAIN OSCILLATOR L-C OSCILLATOR 2 2A FREQUENCY DIVIDER 2 B H) OSCILLATOR REOUENCY 3 FM r DIVIDER H oscum z 4 4A FREQUENCY j DIVIDER L-C OSCILLATOR 6 JA FREQUENCY DIVIDER +56 18 o1 A }o 20 INVENTOR TADAO SAKAI BY K KM AGENT 1 2 TONE OSCILLATOR FOR AN ELECTRONIC MUSICAL The-values of resistors 7 and 8 are selected so that a bias INSTRUMENT current is established in transistor 17 which inhibits oscillation BACKGROUND OF THE INVENTION This invention relates to a tone oscillator used in a musical instrument.

Prior art tone oscillators for electronic musical instruments are typically provided with a sine wave oscillator for each of the frequencies of the musical instrument. The adjustment of these sine wave oscillators is quite troublesome and it has not heretofore been possible to provide a plurality of oscillator circuits having a high degree of stability in operation.

SUMMARY OF THE INVENTION In the tone oscillator of the present invention, the oscillating frequency of the main oscillator is set approximately at the desired frequency and a plurality of divided frequenciesare generated in a plurality of frequency dividers. The outputs of the frequency dividers are applied to a plurality of L-C oscillatingcircuits. The outputs of the tuned L-C oscillating circuits provide a complex musical tone in combination. Each tuned L-C oscillator produces a sinusoidal and a complex output signal.

It is an object of this invention to provide a circuit construction, for the main oscillator, the frequency dividers and the L-C oscillating circuits having a high degree of stability in operation and ease in adjusting the musical tone.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. lis a block diagram showing an illustrative embodiment of the tone oscillator according to this invention, and

FIG. 2 is a diagram showing an embodiment of an L-C oscillating circuit adapted for use in the tone oscillator of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a main oscillator l, and a plurality of frequency dividers 2-5 are connected in series. Frequency divider 2 is energized by the output from main oscillator 1. Frequency divider3 is energized by the output from frequency divider 2. Frequency divider 4 is energized by the output from frequency divider 3. Frequency divider 5 is energized by the output from frequency divider 4.

An L-C oscillator 2A with an output terminal 28 is connected to the output of frequency divider 2 and is energized by the frequency divider; An L-C oscillator 3A with an output terminal 38 is connected to the output of frequency divider 3 and is energized by the frequency divider. An L-C oscillator 4A with an output terminal 48 is connected to the output of frequency divider 4 and is energized by the frequency divider. An L-C oscillator 5A with an output terminal 58 is connected to the output of frequency divider 5 and is energized by the frequency divider.

In FIG. 2, the intermediate terminal of an oscillating coil 16 is connected to a power input terminal 18 and a capacitor 12 is connected across oscillating coil 16. A junction between oscillating coil 16 and capacitor 12 is connected to the collector of a transistor 17 and to an output terminal 20 through a capacitor 13. The other junction between oscillating coil 16 and capacitor 12 is connected to the base of transistor 17 through a capacitor 11.

A resistor 7 is connected between power input terminal 18 and the base of transistor 17 and a resistor is connected between an input terminal 19 through a resistor 6 to the base of transistor 17. A capacitor is connected between the junction of resistor 6 and resistor 10 and ground. A resistor 8 is connected between the base of transistor 17 and the ground. The emitter of transistor 17 is connected to an output terminal 21 trough a capacitor 14 and a resistor 9 is connected between the emitter of transistor 17 and the ground.

The operation of the L-C oscillating circuit shown In FIG. 2 is explained as follows:

in the L-C oscillating circuit. Alternatively, the two resistors are selected to establish a weak oscillation in the L-C oscillating circuit. The values of oscillating coil 16 and capacitor I2 are selected to resonate at a frequency which is nearly equal to the frequency applied to the input terminal of the L-C oscillating circuit from the frequency divider. 1

Under these conditions, applying an output from a frequency divider to transistor 17 via input terminal 19 through resistors 6 and 10 makes'the oscillating circuit become active during-this application and continue to oscillate at the same frequency as that applied to input terminal 19.

A sinusoidalvibration having a frequency which is the same as that applied to input terminal 19 is obtained at output terminal 20.

A positive half cycle of a differentiated waveform of the frequency. divider in question is obtained at output terminal 21.

An integrating circuit comprising resistor 6 and capacitor 15 suppresses the high-frequency components of the pulse wave of the frequency divider in question from appearing at the collector of transistor 17.

Under these circumstances, when oscillating coil 16 and capacitor 12 are fixed and the output frequency of the frequency divider is appliedto input terminal [9, a sine wave with the same frequency as that applied to input terminal 19 is obtained at output terminal 20.

As the oscillating frequencies of L-C oscillators 2A, 3A, 4A and 5A are set substantially the same as the frequencies appearing at theoutput terminals of frequency dividers 2,3, 4 and 5, respectively, an output substantially the same as the frequency of frequency dividers 2, 3, 4 or 5 can be obtained at output terminals 28, 3B, 4B or 58, respectively.

It it is assumed that, in FIG. 1, the dividing ratio is set as 1:2 and the frequency of main oscillator l is f Hz., the output frequency of frequency dividers 2, 3, 4 and 5 will be f/2 Hz., f/4 Hz.,f/8 Hz. and f/ 16 Hz., respectively. Thus, the frequencies present on output terminals 2B, 3B, 4B and 5B naturally become'f/Z Hz., f/4 Hz., f/8 Hz. and f/16 Hz., respectively, where 28, 3B, 4B and 58 represent either terminal 20 or 21 or a signal obtained by mixing the outputs on terminals 20 and 21.

It is noted that many modifications of the combination of dividing ratios and the number of thefrequency-dividers can be employed with the effect that a plural combination of frequencies is obtained.

The stability of the L-C oscillating circuit is determined by the stability of the main oscillator and, therefore, in this invention the stability of the oscillating frequency is high compared with the prior art in which independent sine wave oscillators are utilized, resulting in extreme ease in adjusting the frequency or the tone of the overall stages.

In the circuit shown in FIG. 2, a sinusoidal waveform is obtained' at output terminal 20 and a positive half cycle differentiated, wave of the wave which was applied to input terminal 19 is obtained at output terminal 21. Accordingly, a pluralityof complex waveform can be obtained by combining the waveforms obtained at output terminals 20 and 21 and, therefore, it is possible to utilize the tone oscillator of the present invention as a source of a complex musical tone, rich in harmonics.

Iclaim:

l. A tone generator for an electronic musical instrument, said generator being of the type that includes:

1. a master oscillator;

2. a plurality of serially connected frequency dividers, the

input of the first one of said frequency dividers being connected to the output of said master oscillator, and

3. a corresponding plurality of tuned oscillators connected to the respective outputs of said plurality of frequency dividers, the resonant frequency of each of said tuned oscillators corresponding substantially to the output frequency of its associated frequency divider,

4. wherein the improvement comprises means, in each tuned oscillator, for producing a sinusoidal output at said resonant frequency on a first output terminal and a positive-going, rectified, differentiated output at said resonant frequency on a second output terminal, whereby selective combination of the output signals on said first and second output terminals yields a complex musical tone rich in harmonics.

2. The generator according to claim I, wherein said producing means includes l a transistor;

2. a tuned L-C circuit in the collector-base circuit of said transistor, the power supply for said transistor being connected to a tap on the coil of said L-C circuit; and

'3. means, connected to the base of said transistor, for biasing said transistor to a point just below the point at which said transistor would oscillate, whereby application of an input signal from said frequency divider overcomes said bias and permits said transistor to oscillate and thereby produce said sinusoidal and differentiated outputs.

3. The generator according to claim 1, wherein said producing means includes:

1. a transistor connected in common-base configuration;

2. a tuned L43 circuit connected in the base-collector circuit of said transistor, said tuned circuit having a resonant frequency substantially that of the output from said frequency divider;

3. means, connected to a tap on the coil of said L-C circuit, for supplying a DC potential to said transistor; oscillate;

4. a first and a second resistor serially connected between said supplying means and ground, the juncture of said first and second resistors being connected to the base of said transistor to bias said transistor at a point just below the point at which said transistor would oscillate;

5. an integrating circuit, comprising the series connection of a first capacitor and a third resistor, connected between the output of said frequency divider and ground;

6. a fourth resistor connecting the juncture of said third resistor and first capacitor with the juncture of said first and second resistors, to apply a potential to the base of said transistor to overcome said bias, and permit said transistor to oscillate when an output signal is received from said frequency divider;

7. a second capacitor connected to the collector of said transistor for permitting a first, sinusoidal output signal to be taken from said transistor at a frequency corresponding to the frequency of said output signal from :said frequency divider; and l 8. a differentiating circuit, comprising a fifth resistor, connected between the emitter of said transistor and ground, and a third capacitor connected to the emitter of said transistor, for pennitting a second, rectified output signal to be taken from said transistor, at a frequency corresponding to the frequency of said output signal from said frequency divider, whereby selective mixing of said first and second transistor outputs will yield a complex musical tone rich in harmonics. 

1. A tone generator for an electronic musical instrument, said generator being of the type that includes:
 1. a master oscillator;
 2. a plurality of serially connected frequency dividers, the input of the first one of said frequency dividers being connected to the output of said master oscillator; and
 3. a corresponding plurality of tuned oscillators connected to the respective outputs of said plurality of frequency dividers, the resonant frequency of each of said tuned oscillators corresponding substantially to the output frequency of its associated frequency divider,
 4. wherein the improvement comprises means, in each tuned oscillator, for producing a sinusoidal output at said resonant frequency on a first output terminal and a positive-going, rectified, differentiated output at said resonant frequency on a second output terminal, whereby selective combination of the output signals on said first and second output terminals yields a complex musical tone rich in harmonics.
 2. a plurality of serially connected frequency dividers, the input of the first one of said frequency dividers being connected to the output of said master oscillator; and
 2. The generator according to claim 1, wherein said producing means includes
 2. a tuned L-C circuit in the collector-base circuit of said transistor, the power supply for said transistor being connected to a tap on the coil of said L-C circuit; and
 2. a tuned L-C circuit connected in the base-collector circuit of said transistor, said tuned circuit having a resonant frequency substantially that of the output from said frequency divider;
 3. means, connected to a tap on the coil of said L-C circuit, for supplying a DC potential to said transistor; oscillate;
 3. means, connected to the base of said transistor, for biasing said transistor to a point just below the point at which said transistor would oscillate, whereby application of an input signal from said frequency divider overcomes said bias and permits said transistor to oscillate and thereby produce said sinusoidal and differentiated outputs.
 3. The generator according to claim 1, wherein said producing means includes:
 3. a corresponding plurality of tuned oscillators connected to the respective outputs of said plurality of frequency dividers, the resonant frequency of each of said tuned oscillators corresponding substantially to the output frequency of its associated frequency divider,
 4. wherein the improvement comprises means, in each tuned oscillator, for producing a sinusoidal output at said resonant frequency on a first output terminal and a positive-going, rectified, differentiated output at said resonant frequency on a second output terminal, whereby selective combination of the output signals on said first and second output terminals yields a complex musical tone rich in harmonics.
 4. a first and a second resistor serially connected between said supplying means and ground, the juncture of said first and second resistors being connected to the base of said transistor to bias said transistor at a point just below the point at which said transistor would oscillate;
 5. an integrating circuit, comprising the series connection of a first capacitor and a third resistor, connected between the output of said frequency divider and ground;
 6. a fourth resistor connecting the juncture of said third resistor and first capacitor with the juncture of said first and second resistors, to apply a potential to the base of said transistor to overcome said bias, and permit said transistor to oscillate when an output signal is received from said frequency divider;
 7. a second capacitor connected to the collector of said transistor for permitting a first, sinusoidal output signal to be taken from said transistor at a frequency corresponding to the frequency of said output signal from said frequency divider; and
 8. a differentiating circuit, comprising a fifth resistor, connected between the emitter of said transistor and ground, and a third capacitor connected to the emitter of said transistor, for permitting a second, rectified output signal to be taken from said transistor, at a frequency corresponding to the frequency of said output signal from said frequency divider, whereby selective mixing of said first and second transistor outputs will yield a complex musical tone rich in harmonics. 